DNA Fingerprinting in Human Health and Society

Like the fingerprints that came into use by detectives and police labs
during the 1930s, each person has a unique DNA fingerprint. Unlike a
conventional fingerprint that occurs only on the fingertips and can be
altered by surgery, a DNA fingerprint is the same for every cell,
tissue, and organ of a person. It cannot be altered by any known
treatment. Consequently, DNA fingerprinting is rapidly becoming the
primary method for identifying and distinguishing among individual human
beings.

An additional application of DNA fingerprint technology is the diagnosis
of inherited disorders in adults, children, and unborn babies. The
technology is so powerful that even the blood-stained clothing from
Abraham Lincoln has been analyzed for evidence of a genetic disorder
called Marfan's Syndrome.

The Structure of DNA

Living organisms that look different or have different characteristics
also have different DNA sequences. The more varied the organisms, the
more varied the DNA sequences. DNA fingerprinting is a very quick way
to compare the DNA sequences of any two living organisms.

Making DNA Fingerprints

DNA fingerprinting is a laboratory procedure that requires six steps:

1: Isolation of DNA.
DNA must be recovered from the cells or tissues of the body. Only a
small amount of tissue - like blood, hair, or skin - is needed. For
example, the amount of DNA found at the root of one hair is usually
sufficient.

2: Cutting, sizing, and sorting.
Special enzymes called restriction enzymes are used to cut the DNA at
specific places. For example, an enzyme called EcoR1, found in
bacteria, will cut DNA only when the sequence GAATTC occurs. The DNA
pieces are sorted according to size by a sieving technique called
electrophoresis. The DNA pieces are passed through a gel made from
seaweed agarose (a jelly-like product made from seaweed). This
technique is the biotechnology equivalent of screening sand through
progressively finer mesh screens to determine particle sizes.

3: Transfer of DNA to nylon.
The distribution of DNA pieces is transferred to a nylon sheet by
placing the sheet on the gel and soaking them overnight.

4-5: Probing.
Adding radioactive or colored probes to the nylon sheet produces a
pattern called the DNA fingerprint. Each probe typically sticks in only
one or two specific places on the nylon sheet.

6: DNA fingerprint.
The final DNA fingerprint is built by using several probes (5-10 or
more) simultaneously. It resembles the bar codes used by grocery store
scanners.

Uses of DNA Fingerprints

DNA fingerprints are useful in several applications of human health care
research, as well as in the justice system.

Diagnosis of Inherited Disorders

DNA fingerprinting is used to diagnose inherited disorders in both
prenatal and newborn babies in hospitals around the world. These
disorders may include cystic fibrosis, hemophilia, Huntington's disease,
familial Alzheimer's, sickle cell anemia, thalassemia, and many others.

Early detection of such disorders enables the medical staff to prepare
themselves and the parents for proper treatment of the child. In some
programs, genetic counselors use DNA fingerprint information to help
prospective parents understand the risk of having an affected child. In
other programs, prospective parents use DNA fingerprint information in
their decisions concerning affected pregnancies.

Developing Cures for Inherited Disorders

Research programs to locate inherited disorders on the chromosomes
depend on the information contained in DNA fingerprints. By studying
the DNA fingerprints of relatives who have a history of some particular
disorder, or by comparing large groups of people with and without the
disorder, it is possible to identify DNA patterns associated with the
disease in question. This work is a necessary first step in designing
an eventual genetic cure for these disorders.

Biological Evidence

FBI and police labs around the U.S. have begun to use DNA fingerprints
to link suspects to biological evidence - blood or semen stains, hair,
or items of clothing - found at the scene of a crime. Since 1987,
hundreds of cases have been decided with the assistance of DNA
fingerprint evidence.

Another important use of DNA fingerprints in the court system is to
establish paternity in custody and child support litigation. In these
applications, DNA fingerprints bring an unprecedented, nearly perfect
accuracy to the determination.

Personal Identification

Because every organ or tissue of an individual contains the same DNA
fingerprint, the U.S. armed services have just begun a program to
collect DNA fingerprints from all personnel for use later, in case they
are needed to identify casualties or persons missing in action. The DNA
method will be far superior to the dogtags, dental records, and blood
typing strategies currently in use.

"The promise and pitfalls of molecular genetics." Science. July 10, 1992.

Issued in furtherance of Cooperative Extension work, Acts of Congress of
May 8 and June 30, 1914, in cooperation with the U.S. Department of
Agriculture and Cooperative Extension Services of Illinois, Indiana, Iowa,
Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio,
South Dakota, and Wisconsin.